1. Field of the Invention
The present invention relates to a data processing system. More particularly, it relates to a data processing system having a system control register group for storing system control data and a copy register group for storing data copied from the system control data, wherein machine stoppage due to an error only in the copy register, can be prevented.
2. Description of the Prior Art
A data processing system conventionally comprises an instruction control unit for controlling the system operation and a storage control unit for storing data used for the system operation. The instruction control unit has a system control register group for storing system control data. The storage control unit has a copy register group for storing data copied from the system control data. The copy register group is used, for example, for converting address signals between logical address signals and real address signals in dynamic address translation (DAT) of virtual machines.
During operation, a change in the contents in the system control register group is accompanied by a corresponding change in the contents in the copy register group.
In the case of an error anywhere else except in the groups, either a retry process for repeating the instruction which has caused the error or a machine check interruption process may be carried out. If the error is corrected during the retry operation or during the machine check interruption, the operation continues and subsequent instructions are executed. If the error is not corrected by the retry operation, a machine check interruption is carried out. If the error is not corrected during the machine check interruption, the operation is terminated to reach a machine stop status.
An error in the system control register group or in the copy register group, however, is serious, regardless of whether it is a soft error or a hard error, since system control is effected by those groups. Therefore, if an error occurs in the register groups, a machine check interruption process is carried out, not a retry process. If the error is not corrected during the machine check interruption process, the error is recognized as a hard error, i.e., an uncorrectable error, and the data processing system falls into a machine stop status.
It is reasonable for an uncorrectable error in the system control register group to lead to a machine stop status. A soft error in the copy register group, however, does not always have to lead to a machine stop status when no error is present in the system control register group and the error in the copy register group is produced during copying. In the prior art, however, soft errors in the copy register group always lead to a machine stop status even when no error is present in the system control register group.